Application of the molecular test PCR multiplex for identification of Mycobacterium bovis BCG strains

: In our last paper (18) we described the problem of proper microbiological identification of BCG strains and how important is distinguishing vaccine strain from virulent strains of Mycobacterium tuberculosis complex. We have suggested the modern algorithm of BCG strains identification including mycolic acids profile by HPLC and 14C PZA resistance methods. These methods allowed us to made fast and accurate microbiological identification of side effects of BCG vaccine in the children. Identification of BCG by HPLC is possible within one working day compared with 3-4 weeks required for conventional methods. However both methods need very expensive instruments like HPLC and/or Bactec-460 Tb radiometric system. Presently we have evaluated molecular test based on the analyzis of the region RD1 encoding a 9.5-kb fragment. This fragment is deleted in all BCG substrains (6) and present in all human and bovine virulent strains. To evaluate this method for the rapid and specific detection of BCG, a large strain collection (32 strains) representating M. bovis BCG (vaccine strains and strains isolated from the children in case of adverse reactions after vaccination) M. bovis and M. tuberculosis from own collection was analyzed. RD1 was present in all 15 M. tuberculosis and M. bovis tested strains and deleted in 17 of 18 BCG strains. The multiplex PCR method was 100% sensitive and specific for the identification of BCG among strains of the Mycobacterium tuberculosis complex. Multiplex PCR can be used as a diagnostic test and has significant advantages over existing methods.